Kashanov, Runis (2023) Comparison of Austroads Guidelines for Lime Stabilisation of Highly Organic Black Soil. [USQ Project]
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Abstract
Expansive clay soils, often referred to as ’Cracking Clays’ and ’Black Soils’, are prevalent in the inland regions of Queensland, Australia, covering around 28% of the state’s land. These soils are well known for their high shrink-swell capacity and plasticity, expanding and transitioning from dry and cracked to slippery and yielding when soaked. Their reactivity makes them an undesirable subgrade material for road construction and rehabilitation, which requires specialised approaches like advanced drainage design, material replacement or lime stabilisation.
This follow-up study, based on pavement investigations carried out by the Queensland Department of Transport and Main Roads in 2017, examined black soil samples from a site 40 km south of Cooyar, QLD, mixed with lime following the Austroads (2019) Guide to Pavement Technology Part 4D. After 28 days of curing, this study assessed the Unconfined Compressive Strength (UCS) and soaked California Bearing Ratio (CBR) to determine the causes of the problems observed during the original DTMR investigation and compare the Austroads (2019) mix design methods.
The results showed that it was highly organic and responded well to what Little (1995) has termed a lime modification, indicated by a decrease in Maximum Dry Density and CBR Swell, and an increase in Optimum Moisture Content and CBR with increasing lime content. However, the soil was resistant to lime stabilisation, with UCS results of 0.3 or 0.4 MPa at all lime contents suggesting a negative impact of organic carbon content on the pozzolan fraction and reduction in the production of C-S-H and C-A-H gels. This indirect comparison of the two Austroads (2019) methods has shown that the comparison of CBR results before and after lime incorporation is not a reliable measure of the success of a pozzolanic reaction and only identifies that there has been a cation exchange between the surface of clay particles and calcium ions.
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Statistics for this ePrint Item |
| Item Type: | USQ Project |
|---|---|
| Item Status: | Live Archive |
| Faculty/School / Institute/Centre: | Current – Faculty of Health, Engineering and Sciences - School of Engineering (1 Jan 2022 -) |
| Supervisors: | Seligmann, Hannah |
| Qualification: | Bachelor of Engineering (Honours) (Civil) |
| Date Deposited: | 29 Sep 2025 23:21 |
| Last Modified: | 29 Sep 2025 23:21 |
| Uncontrolled Keywords: | soils; road; pavement |
| URI: | https://sear.unisq.edu.au/id/eprint/52961 |
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